Push bench for drawing tubes



2 Sheets-Sheet 1 Filed April 17, 1934 Inventor:

Dec. 17,1935. E, RBR 2,024,185

PUSH BENCH FOR DRAWING TUBES Filed April 17, 1934 2 Sheets-Sheet 2 INVENTOR a); AT oRNEYb Cil Patented Dec. 17, 1935 UNITED STATES lPATENT oFFIcE Application April 17, 1934, Serial No. 721,019 In Germany February 13, 1933 5 Claims.

'I'he invention relates to push benches, such as used in the production and further Working up of tubes and hollow bodies,

Most of the tubev push benches used now-a days have a toothed rack drive. The toothed rack is followed by a long shaft driving the mandrel. The shaft must be carefully guided throughout its entire length in order to prevent its lateral bending out or curvature owing to the comparatively strong pressure to which it is subjected While the hollow body is being pushed through the drawing rings. The numerous guiding means devised for the purpose are either carried along in a longitudinal direction one after another by the forward motion of the shaft towards the drawing ring bed or moved laterally out of the reach of the toothed rack section. The just mentioned shaft guides have proved obstructive when the output of this type of bench is increased in regard to tube dimensions, especially when the drawing speed is accelerated. Even with the best designs it is impossible to accelerate the speed of the shaft to such an extent as will be desirable to ensure proper working of the hot material.

The present invention does away with these drawbacks. In applying the new process, guides for the shaft may be generally dispensed with altogether. In cases where this is impracticable, the lateral forces acting on the guides may be at least reduced to such a degree that the guides can .be designed much lighter and more mobile.

According to the invention the push bench is driven hydraulically, pneumatically, by compressed gas or the like. `For this purpose, a hydraulic, pneumatic or gas driven press is inserted into the push bench in such manner, that its cylinder is pushed,v together with the mandrel and theblank mounted on the mandrel, through the drawing bed.

This process is carried out preferably in the manner that tubular thrust bars or mandrels are used, and the push bar itself is formed like a movable cylinder which is lled with the pressure medium. In this case the push bar is subject throughout the whole working process only to tensile stresses instead of compression or buckling stresses which prevail in the known push benches for tube drawing used up to now. Thus the push bar irrespective of its diameter or length, is

maintained in a stretched condition throughout sible with the usual processes applied up to now. The process is applicable too for maximum stroke lengths. y

. My invention is illustrated in the accompanying` drawings which show several modifications of 5 the manner in which the invention may be reduced to practice. In these drawings- Fig. 1 represents a hydraulic push bench with xed dies, shown semi-diagrammatically in horizontal section and at the beginning o1 the stroke. 10

Fig. 2 shows semi-diagrammatically a similar section, showing the push bar after the completion of its stroke through all the drawing dies.

Fig. 3 shows a horizontal section in somewhat larger scale through the portion of the bench 15 shown in Figs. 1 and 2 in which the plunger guiding devices are located.

Fig. 4 shows a transverse section through the bench portion l, 4 in Fig. 3, and

Fig. 5 shows a transverse section in larger scale 20 through a modied push bench employing draw rolls instead o! drawing dies.

'I'he push bench shown in Figs. 1 through 4 consistsin its essential features vof a bench bed z on which the drawing dies a are spaced certain distances apart given by experience. The push bar f serves as the pushing device. In the present example this bar is formed by a longitudinally movable long cylinder'into which the pressure medium is supplied. By forming this push bar as a hollow cylinder the effect is obtained that the bar is subject only to tension stresses instead of buckling stresses as is the case in the ordinary prior art push benches. This occurs because the effective force of the pressure fluid now always acts directly against the interior of the front end of the bar, instead of the force acting against the rear end of the bar as in the prior art devices. Thel push bar is so designed in size and length that it can pass together with the blank to he drawn through all drawing dies. Since by the internal pressure exerted by4 the medium it is held in stretched condition during its entire work stroke, the type of guides heretofore used to prevent buckling due to thepushing forces may be entirely omitted. During its work kand return stroke, Vthe push bar slides on a xed hollow plunger i on which it is mounted fluid-tight by' means of a stuilng box h which is provided at the'rear end of the push bar. Plunger i terminates at its front end in the push bar, at which point the fluid is supplied through the plunger into the bar, and

g at its rear end in the plunger head lc. The plunger head is connected by means of conduits,lshown in dotted lines, with a pressure fluid system, and

further contains all control devices necessary for the admission of pressure fluid. Since the construction of these control devices is immaterial for the present invention they have been omitted in the drawings.

Behind plunger head k is provided a windlass w whose cables q are connected with the stuliing box h of push bar f. This windlass serves for retracting the push bar into its initial position shown in Fig. 1 after it has been thrust forward during the working stroke. Plunger i is surrounded by a special supporting frame l which carries supporting bell cranks o held by spiral springs p (indicated by dash-dot lines in Fig, 3) in a position clearly shown at the left hand side of Figs. 2 and 3, in which the free ends of these bell cranks bear against the plunger i so that they support the latter from four sides as is shown clearly in Fig 4. When push bar f is retracted these supporting bell cranks are lifted from their plunger supporting positions against the tension of springs p by the stuli'ing box as is shown in Figs.

-2 and 3 at the right-hand side of stuiilng box h.

In order to effect this change in position of these bell cranks, the stuiling box is cone-shaped at both ends as shown in detail in Fig. 3 so that it can move these bell cranks when it slides past them in either direction.

Near the right hand end of the supporting frame -l are provided two supporting rolls g which serve for supporting the push bar and the plunger i so as to hold these elements in central axial aline ment with the drawing axis of the bench. Push bar f is provided at its forward end with a tip e with which it engages the mandrel d on which in turn the hollow blank is placed when the drawing commences. A stop collar d' is provided on tip e for limiting the length for which thevmandrel extends over tip e. The hollowend product resulting from drawing the blank b is denoted in Fig. 2 with e. The supporting frame l for the plunger i is provided with longitudinal guide grooves m (see Fig. 4) in which engage guides n. provided on the push bar.

The device works in the following manner: At the beginning of the working stroke the push bar tip e, mandrel d and blank b are in the position shown in Fig. 1. If now pressure fluid is supplied through the plunger head k and through the plunger i into the interior of push bar f, the latter moves to the right whereby the push bar -tip e rst engages the mandrel d, which latter slides against stop collar d. On further motion to the right the mandrel penetrates into the blank and carries the latter along successively through the several drawing dies a-in which the blank 'Ls reduced to size emerging from the last die at the right hand end of Fig. 2 in elongated form c. The push bar has now completed its work stroke and has thereby run through all drawing dies a. During this stroke bell crank o, in the manner described hereinbefore, after first sliding' with their inner ends along on the push bar f and after being lifted when the stuing box passes them, iinally assume the position shown at thelei't hand end of Fig. 3 in which their inner ends rest against the plunger i, supporting the latter in central position. In this manner bending of the plunger due to its own weight and due to the buckling forces exerted by the pressure fluid against its annular inn er end surface is prevented.

In order to secure an effective support of the plunger in this manner, the supporting bell cranks ol are spaced along the plunger length at uniform intervals asis shown in Fig. 2. While in the present illustration a simple bell crank form of these supporting elements o is shown, their form may vary to suit the particular construction of the bench, the more or less diagrammatic illustration of Fig. 3 of the functioning of these supports merely indicating the general idea of the provision of movable supports for the plunger.

The hollow push bar is stopped at the end of its outward thrust so that it may not slide of! stroke the speed of the push bar may gradually be retarded by suitably throttling the outflow of the pressure medium.

It will be seen that in this manner, during the work stroke as well as during the return stroke and during 'the retardation of the speed during the return stroke, the push bar is at all times subject solely to tensile stresses, and is thus prevented irom buckling. It is,.of course, not always necessary to support the plunger by means such as are described with reference to Figs. 1 to 4, depending entirely on the diameter and length of the plunger. In case of small diameters and great lengths such supports will always be necessary.

With these hollow and comparatively light cylindrical push bars according to this invention all sorts of tubes can be very easily drawn with much thinnerwalls than is possible by the methods used heretofore. Furthermore, this novel push bench besides is particularly suited for drawing of tubes of very great length, also in case of comparatively small diameter tubes. Furthermore, in case of already drawn or rolled tubes the diameter and wall thickness can be easily changed in one stroke by means of a number of successively spaced drawing dies, and in one heat. Of course, this push bench may also be used for cold drawing.

Since push benches operated according to-the present invention by a pressure medium admit of d -longer strokes for a given bench length than can be realized with the present day benches, the drawing dies may be replaced also by drawing rolls, the arrangement of which usually demands a greater overall length of the machine bed. Owing to the much shorter bench. length required according to the present invention the use of drawing rolls would not involve an inconvenient overall length of the bench.

The manner in which drawing rolls may be arranged in place of dies is shown in Fig. 5 in an enlarged cross-section through a modified push bench. 'In this figure 20 represents the bench bed in which are journalled two pairs of parallel shafts 2| and 22. The shafts of each pair are disposed on diametrically opposite sides of the blank 23 to be drawn or rolled, and the two shaft pairs are disposed at right angles to one another as shown. The shafts of each pair carry gear wheels which are in mesh with one another. Thus for instance the pair of meshing gears 24 is mounted on the shaft pair 2l and. the pair of meshing gears 25 is mounted on the shaft pair 22. The shafts of each. pair carry suitably profiled rolls which surround. the blank 23 as is shown in Fig. 5, where the rolls 26 are driven by the shaft pair 2| and the rolls 21. are driven b y the shaft pair 22. Each shaft pair is driven by a`l positive drive 28, 29 respectively through an overrun coupling 30, 3| respectively. This' overrun coupling is provided for each shaft pair in order to prevent during the rolling operation, and in case the speed of the push bar should not'exactly coincide with the peripheral speed of the rolls, undue sliding movement between the tube and the peripheral surfaces of the positively driven rolls. Through the overrun clutches it becomes possible for the rolls to permit the free forward motion of the blank due to the pushing by the push bar. These overrun clutches are of standard construction, and their details arev therefore omitted from the description. By the provision of such overrun clutches a higher output becomes possible without any danger of tearing the blank, and without the production of thicker portions in the blank wall in the proximity of the blank ends which frequently occur in the ordinary type of reducing mill. It is, of course, also possible to equip a push bench such as is shown in Figs. 1 through 4 with drawing dies as well as with rolls,

`such as are shown in Fig. 5. When positively driven rolls such as are. shown in Fig. 5 are employed it may be of advantage to adapt the maximum working pressure of the pushing device to the admissible tensile strength of the tube to be drawn.

I claim:

1., A tube push bench comprising a. bench bed having at least one die element xed on it in axial alinement with the drawing axis of the bench, and through which the blank is pushed, a hollow cylindrical push bar closed at its front end and having means for supplying pressure fluid from the rear end to its interior, so that the effective force of the pressure fluid acts d1- rectly against the interior of the bar front end, said bar being arranged in axial alinement with said die element to follow the blank through the die element, and a mandrel disposed at and extending a suitable distance over the front end of said bar and shaped to operatively engageI said blank, to push and follow it together with said push bar through said die element.

2. A tube push bench comprising a bench bed having at least one die element ilxed on it in axial alinement with the drawing axis of the bench, and through which the blank is pushed, a hollow cylindrical push bar closed at its front end and actuated by a pressure iluid supplied from the rear end to its interior and arranged in axial alinement with said die element to follow the-blank through the die element. and a mandrel disposed at and extending a suitable distance over,the front end of said bar and shaped to operatively engage said blank to push and follow it together with said push bar through said die element, and a fixed plunger disposed in said push bar for guiding the bar during its movement through said die element.-

3. A tube push bench comprising a bench bed having at least one die element fixed on it in axial alinement with the drawing axis of the bench, and through which the blank is pushed, a hollow cylindrical push bar closed at its front 5 end and actuated by a pressure fluid and arranged in axial alinement with said die element to follow the blank through the die element, and a mandrel disposed at and extending a suitable distance over the front end of said bar and shaped to operatively engage said blank to push and follow it together with said pushfbar through said die element, and a fixed hollow plunger disposed in said push bar for guiding the bar during its movement through said die element and for supplying l5 pressure iluid into said bar, whereby the effective force of the iluid acts directly against the interior of the front end ofthe bar, and a frame fixed to said bed and surrounding said push bar and plunger, `for supporting said latter elements in theiraxial alinement.

4. A tube push bench comprising a bench bed having at least one die element xed` on it in axial alinement with the drawing axis of the bench, and through which the blank is pushed, a hollow cylindrical push bar closed at its front end and actuated 'by a pressure fluid and arranged in axialalinement with said die element to follow the blank through the die element, and a mandrel disposed at and extending a suitable distance over the front end of said bar and shaped to operatively engage said blank,.and a xed hollow plunger disposed in said bar for guiding the bar during its movement through said die element and for supplying pressure uid into said is thrust through the die element during the drawing operation. 5. A tube push bench comprising a bench bed J having a plurality of ring dies spaced along the bench bed in axial alinement with the drawing axis of the bench, and through which the blank is pushed, a hollow cylindrical push bar closed at its front end and having means for supplying pressure fluid from the rear end to its interior, so that the effective force of the pressure fluid acts directly against the interior of the bar front end,

said bar being arranged in-axial alinement with y said die element to follow the blank through the A die element, and a mandrel disposed at and extending a suitable-distance over the front end of said bar and shaped to operatively engage said blank, to push and follow it together with said no push bar through said dies.

EWALD RBER. 

